1. Field of the Invention
This invention relates to the methods and apparatus for purifying and sanitizing water using a combination of halogenation and introduction of microbiocidal metal species into the water. More particularly, the invention relates to the systems and methods for combining purification by chlorination and the introduction of biocidal metal ions into the water using a single purification unit that is easier to install, operate, and maintain than are existing systems.
2. Description of Related Art
Purification of water by chlorination has been carried out for some time. The introduction into water, in particular pool water, of compounds that dissolve or hydrolyze to form hypohalic acid, hypohalite ions, or both have known utility in disinfecting the water (and whose use is typically known as “chlorinating” the water). Chlorination is widely used to protect swimmers and bathers in swimming pools, hot tubs, spas, and the like. It is a relatively safe, effective, and reliable method of water purification, and is familiar to many pool owners.
However, effective use of chlorination requires a rather high level of skill and involvement on the part of the pool or spa owner. The water chemistry must be carefully monitored and adjusted to maintain appropriate chlorine levels. Because the amount of hypochlorite ion in the water degrades over time, the chlorine levels must be constantly replenished by addition of fresh chlorination chemicals. This requires that the pool owner frequently monitor chlorination levels and frequently handle, measure, and add chlorination chemicals. Lack of adequate care or insufficient skill in handling these chemicals can lead to an over- or under-chlorinated pool.
Highly chlorinated pool water is often uncomfortable to, and is thought to possibly have adverse effects on the health of, swimmers and bathers, decreases the useful life of swimwear, etc. For example, overly chlorinated water can cause burning sensations in the eyes and other mucus membranes, and is associated with a characteristic odor that some find unpleasant. On the other hand, insufficient chlorine levels can allow the growth of pathogenic and nonpathogenic organisms to occur, which can create health risks and poor pool appearance.
In addition, hypochlorite generating chemicals are strong oxidizers, which can cause burns to human skin if not handled properly. It is also possible that exposure to aqueous hypochlorite generating chemicals can cause metal parts to corrode more quickly.
For all of these reasons, alternatives to chlorination, or at least purification techniques the decrease the amount of chlorination that must be used, have long been sought. The introduction of microbiocidal metals into water to sanitize it has also been suggested for and used in various water purification applications, such as in pools and spas. In particular, various methods of introducing metal ions, such as silver ions or copper ions, into the water have been proposed. The use of these ions to purify, e.g., pool water, results in decreased need for chlorination. One method of introducing such ions into water that has been proposed involves the use of sacrificial electrodes containing metals corresponding to the desired ions, including alloys of silver and copper, and electrolytically dissolving the metals into the water. Other methods include contacting the water with substrates that have been coated or impregnated with metal, soluble metal salts, or some combination thereof. These methods can be difficult for pool owners to control, and as a result, can sometimes provide unreliable control of metal delivery, and can cause stained surfaces when too much metal has been delivered, or result in insufficient sanitation when too little metal has been delivered.
There remains a need in the art for a water purification system that provides the benefits of both metal ion purification and chlorination techniques, that is easy to install, maintain, and operate, that provides automatic control of chlorine levels in the pool, and that requires less handling of chlorinating chemicals by the pool owner.